A method for estimating a position of a target by using an image acquired from a camera is generally called a camera modeling technique. According to the camera modeling technique, a relationship between a position on a two-dimensional image and that on a three-dimensional space may be established.
In addition, according to the camera modeling technique, a concept of “view-path” may be introduced. The “view-path” represents a virtual straight path connecting a position of a camera with which an image is taken and that of a target. If physical phenomena such as atmospheric refraction are not considered, the view-path is generally modeled as a straight line. One of the most important purposes of the camera modeling technique is to get information on the accurate position of the target.
FIG. 4 shows a method for estimating a position of a target by using an image acquired from a camera according to an example of the prior art.
By referring to FIG. 4, a point C (xn, yn, zn) represents a position of the camera in three-dimensional coordinate system and a point O (x0, y0, z0) shows a point where a view-path, which is a virtual straight line passing through the position of the camera and that of a target 410, and the geoid intersect in the three-dimensional coordinate system.
More specifically, by referring to FIG. 4, a ray tracing algorithm is illustrated as a method for estimating the position of the target 410 by using the image acquired from the camera. According to the ray tracing algorithm method 440, a point where the view path and the altitude of the terrain intersect can be searched by using iterating operation. However, it has a drawback in that a lot of iterating computations are required, as the case may be. Specifically, if a slope of the earth surface is larger than an incidence angle of ray, a tracking path caused by the iterating operation may not converge on a point so that there is a possibility that computations can be infinitely iterated. Because such a problem frequently occurs to terrains whose actual altitude values 420 are sharply changing and there are, in fact, many terrains whose actual altitude values 420 are sharply changing, there are many cases that the position of the target cannot be estimated by using the ray tracing algorithm.
In addition, if the position of the target is estimated by using multiple pixels, the number of iterating operation per pixel may be different so that multi-processing cannot be executed. Thus, there is a problem of failing to improve the speed of calculation for estimating the position of the target.